The internal energy of an ideal gas is given by:
[tex]U= \frac{k}{2}nRT [/tex]
where
n is the number of moles
R is the gas constant
T is the absolute temperature of the gas
k=3 for monoatomic gases, k=5 for diatomic gases
In this problem, we have n=3.0 mol of a diatomic gas (k=5) at T=288 K. Substituting these numbers into the equation, we find the internal energy of the gas:
[tex]U= \frac{5}{2}(3.00)(8.31 J/mol K)(288 K)=17950 J [/tex]